Intravascular blood pump having multilayer coreless coils

Abstract

To provide an intravascular blood pump for insertion into the patient's heart.SOLUTION: A blood pump comprises a slotless permanent magnet motor contained in a housing, the motor having p magnet pole pairs and n phases, where p is an integer greater than zero, and n is an integer greater than or equal to 3. The motor comprises a stator extending along a longitudinal axis of the housing and having 2np coils wound to form two coils per phase per magnet pole pair. The stator comprises inner and outer windings each comprising np coils electrically connected such that a current flowing through the coils is in a same direction, the coils of the outer winding arranged on an outer surface of the coils of the inner winding.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 868,530, filed June 28, 2019, and incorporated herein by reference.

[0002] Technical Field The present technology relates to an intravascular blood pump system including a permanent magnet motor and a stator having a coil. [Background technology]

[0003] background Intravascular blood pumps, such as the Impella® pump by Abiomed, Inc. of Danvers, MA, are rapidly becoming the current standard for ventricular assist devices. Impella® pumps currently include the Impella 2.5® pump, the Impella 5.0® pump, the Impella CP® pump, and the Impella LD® pump. These pumps are inserted percutaneously into the patient through a single access point (e.g., radial, femoral, axillary access) so that the pump head can be placed within the left ventricle of the patient's heart via a small diameter (6-7 Fr) catheter. The pump head includes an electric motor that includes a stator configured to magnetically interact with a rotor to rotate it, thereby effecting a volumetric flow of blood through the rotor and, therefore, through the patient's heart.

[0004] Currently, Impella® pumps can deliver blood at flow rates of about 1.0 to about 6.0 liters per minute (lpm). However, with the use of Impella® in an increasing number of surgical procedures, there is an increasing demand to generate even more blood flow than these levels. This essentially means that the electric motor needs to produce a higher rotor speed. However, due to the small geometries involved, increasing rotor speed has several implications that may affect the operation of such small sized pumps. For example, increasing rotor speed may be accompanied by increased heat generation (Joule heating) in the electric motor. Since the device is inserted percutaneously into the heart, such increased heating may have serious implications. Another consideration is the resistive load posed to the device; modifications made to the electric motor to achieve higher flow rates may lead to higher resistive losses.

[0005] Various techniques have been used to increase the torque coefficient and / or efficiency of motors, including increasing the number of winding turns and packing density of the coils within the motor. However, such topologies are limited by constraints imposed on the motor, such as the size (e.g., diameter and / or length) of the motor. This has led to the implementation of post-processing methods, such as mechanically squeezing the coils to adhere to the motor dimensional constraints; however, such methods compromise the reliability of the motor, for example by damaging the insulation of the wires forming the coils, leading to short circuits.

[0006] Given the above-mentioned shortcomings of the state of the art, a significant need exists for increasing the flow rate produced by an electric motor while maintaining or increasing the efficiency of the motor. Summary of the Invention

[0007] Quick Overview Disclosed herein is a device for addressing the various problems and shortcomings of the state of the art discussed above. More specifically, disclosed herein is an intravascular blood pump for insertion into a patient's heart. The blood pump of the present invention comprises an elongated housing having a proximal end connected to a catheter and a distal end coupled to a pump; the housing has a longitudinal axis. The blood pump comprises a slotless permanent magnet motor contained within the housing, the motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3. The motor comprises a stator having 2np coils extending along the longitudinal axis of the housing and wound to form two coils per phase per permanent pole pair. The stator comprises an inner winding having np coils, one coil from each phase being arranged next to a coil from a different phase in phase order for each pole pair, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross section of the stator, the inner winding having an outer surface. The stator also comprises an outer winding having np coils arranged on the outer surface of the inner winding, the coils from each phase of the outer winding being circumferentially aligned with the coils from the inner winding having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator. Within the stator, the coils of the same phase for each pole pair are connected such that the currents flowing through them are in the same direction. The coil windings described herein are formed from magnet wire. Magnet wire is well known to those skilled in the art and will not be described in detail herein. In addition, the motor includes magnets supported to rotate upon magnetic interaction with the stator, thereby promoting the flow of blood through the pump.

[0008] In another aspect, a slotless permanent magnet electric motor is provided having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3, the motor having a longitudinal axis. The motor includes a stator extending along the longitudinal axis of the housing and having 2np coils wound to form two coils per phase per permanent pole pair. The stator includes an inner winding having np coils, in which one coil from each phase is positioned next to a coil from a different phase in a phase order per pole pair, the arrangement repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) around a cross section of the stator, and the inner winding has an outer surface. The stator also includes an outer winding having np coils disposed on the outer surface of the inner winding, with each phase of the outer winding being circumferentially aligned with the inner winding coils having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator. Within the stator, the coils of the same phase for each pole pair are connected such that the currents flowing through them in the same direction. Additionally, the motor includes magnets supported to rotate upon magnetic interaction with the stator, thereby promoting rotation of the rotor.

[0009] In some embodiments, the outer winding comprises at least the same number of winding turns as the inner winding. In certain embodiments, each coil comprises two layers of magnet wire each extending longitudinally along the length of the stator. In some embodiments, the magnet wire in each coil is positioned next to each other in sequence along the span of the coil. In further embodiments, the inner winding of a coil establishes a uniform base upon which the outer winding of the coil is superimposed. In other embodiments, the coils of one phase are connected to the coils of the other phase in either a star or delta configuration. In some embodiments, the coils of each phase are connected in either series or parallel.

[0010] In certain embodiments, the 2np coils comprise any one of a helical winding, a rhombic winding, a conventional winding, and a hybrid winding. In further embodiments, the motor comprises a 3-phase, 1-pole pair machine. In other embodiments, the motor comprises a 6-coil, 2-pole machine, with each coil spanning a mechanical angle of 120 degrees around the cross section of the stator. In some embodiments, the rotor pumps blood at a flow rate of about 1.0 lpm to about 6.0 lpm. In other embodiments, the pump may be inserted into the right ventricle of the patient's heart. In further embodiments, the pump may be inserted into the left ventricle of the patient's heart.

[0011] The arrangement in which the 2np coils are wound as a double winding with np coils in the inner winding and np coils in the outer winding to form two coils per phase per pole pair allows for more wire to be used in the available space in the electric motor, thereby allowing for better utilization of the motor space design, which improves the efficiency of the motor compared to motors with single-winding stators.

[0012] In a further aspect, a method is provided for forming a stator for use in a slotless permanent magnet motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3, the stator having 2n coils extending longitudinally and wound to form two coils per phase per permanent pole pair, the method includes forming an inner winding having n coils, one coil from each phase being positioned next to a coil from a different phase in a phase order per pole pair, the arrangement being repeated around a circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (n) degrees around a cross section of the stator, and the inner winding has an outer surface. The method then includes forming an outer winding having n coils disposed on an outer surface of the inner winding, the coils of each phase of the outer winding being circumferentially aligned with the coils of the inner winding having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (n) degrees around the cross section of the stator. The method then includes electrically connecting the coils of the same phase for each pole pair such that current flows through the coils in the same direction.

[0013] In some embodiments, the method further includes forming the outer winding such that the outer winding has at least the same number of winding turns as the inner winding. In certain embodiments, the method also includes forming the coils such that each coil has two magnet wire layers each extending longitudinally along the length of the stator. In other embodiments, the magnet wire in each coil is arranged next to each other in sequence along the span of the respective coil. This allows for precise ordering and compact placement of the magnet wire within the coils of the stator, which leads to a minimal coil thickness that does not require mechanical squeezing to fit within the yoke of the electric motor. The stator is the combination of the coil and yoke. The thickness of the stator is the combined thickness of the coil thickness and the yoke thickness. The coil thicknesses described herein exclude the yoke thickness. The precise ordering and compact placement of the coils increases the reliability of the dual-wound stator since there is no risk to the integrity of the insulation around the wires forming the windings. This minimum coil thickness also allows larger rotor magnets and / or thicker magnet steel yokes to be used in the electric motor, thereby enabling a higher efficiency motor compared to motors using stators with randomly wound multi-layer magnet wire.

[0014] In some embodiments, the method includes connecting the coils of one phase to the coils of the other phase in either a star or delta configuration. In certain embodiments, the method includes connecting the coils of each phase in either series or parallel. In other embodiments, the method includes forming 2np coils with coil windings selected from any one of helical, rhombic, conventional, and hybrid. In some embodiments, the stator is suitable for use in a motor having three phases and one pole pair. In certain embodiments, the stator is suitable for use in a six coil, one pole pair motor, with each coil spanning 120 mechanical degrees around the cross section of the stator. [Brief description of the drawings]

[0015] These and other objects and advantages will become apparent from the following detailed description considered in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.

[0016] [Figure 1] 1 illustrates an exemplary cross-section of an intravascular blood pump according to one embodiment of the present disclosure. [Diagram 2] Figures 2A-2D show exemplary winding patterns for individual turns in a coil, as known in the art, that may be used in the blood pump of Figure 1. Figures 2E-2H show exemplary completed coil winding patterns formed by a coil having individual turns shown in Figures 2A-2D. [Diagram 3] 2 shows an exemplary cross section of a three-phase, single-wound stator, with each phase implemented with a single helical coil, for use in the blood pump of FIG. 1. [Figure 4] 2 illustrates an exemplary cross-section of a three-phase dual-winding stator, with each phase implemented with a dual helix coil, according to one embodiment of the present disclosure, for use in the blood pump of FIG. [Diagram 5] 5 illustrates an exemplary cross-section of the stator of FIG. 4 used in the blood pump of FIG. 1 according to one embodiment of the present disclosure. [Figure 6] FIGURE 6A shows an example circuit diagram illustrating lead connections for the single-winding stator of FIGURE 3. FIGURE 6B shows an example circuit diagram illustrating lead connections for the dual-winding stator of FIGURE 4 with coils of the same phase connected in series according to one embodiment of the present disclosure. FIGURE 6C shows an example circuit diagram illustrating lead connections for the dual-winding stator of FIGURE 4 with coils of the same phase connected in parallel according to one embodiment of the present disclosure. [Figure 7] 2 illustrates an exemplary cross-section of the blood pump of FIG. 1 using a dual-winding stator for an electric motor having three phases and two pole pairs according to one embodiment of the present disclosure. [Figure 8] 2 illustrates an exemplary cross-section of the blood pump of FIG. 1 using a dual-winding stator for an electric motor having five phases and one pole pair according to one embodiment of the present disclosure. [Figure 9] Figure 9A illustrates an example random-wound multi-layer stator with a wire winding sequence used to form it, and Figure 9B illustrates an example dual-wound stator with a wire winding sequence used to form it, according to one embodiment of the present disclosure. [Figure 10] Figure 10A shows an image of a randomly wound multi-layer stator formed using the wire winding sequence of Figure 9A, and Figure 10B shows an image of a dual-winding stator formed using the wire winding sequence of Figure 9B, according to one embodiment of the present disclosure. [Figure 11] 4 and 9B according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Detailed Description Various aspects of the present disclosure will be described in detail with reference to the drawings, in which similar reference numerals refer to similar or identical elements. It should be understood that the disclosed aspects are merely examples of the present disclosure, which may be embodied in various forms. Well-known functions or constructional modes are not described in detail to avoid obscuring the present disclosure with unnecessary details. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but only as a basis for the claims and as a representative basis for teaching those skilled in the art to use the present disclosure in various ways in virtually any structure with reasonably detailed structures.

[0018] Certain exemplary aspects will be described so that the devices described herein may be fully understood. Although the aspects and features described herein are specifically described for use in connection with an intravascular blood pump, it will be understood that all components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to other types of procedures requiring an efficient electric motor.

[0019] The devices and methods described herein relate to an intravascular blood pump for insertion into a patient's heart. The blood pump of the present invention comprises an elongated housing having a proximal end connected to a catheter and a distal end coupled to a pump, the housing having a longitudinal axis. The blood pump comprises a slotless permanent magnet motor contained within the housing, the motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3. The motor comprises a stator extending along the longitudinal axis of the housing and having 2np coils wound to form two coils per phase per permanent pole pair. The stator comprises an inner winding having np coils, one coil from each phase arranged next to a coil from a different phase in phase order for each pole pair, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross section of the stator, the inner winding having an outer surface. The stator also comprises an outer winding having np coils arranged on the outer surface of the inner winding, the coils from each phase of the outer winding being circumferentially aligned with the coils from the inner winding with the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator. Within the stator, the coils of the same phase for each pole pair may be connected in series or parallel such that the currents flowing through them are in the same direction. In addition, the motor includes magnets supported to rotate upon magnetic interaction with the stator, thereby promoting the flow of blood through the pump.

[0020] The intravascular blood pump of the present disclosure uses an electric motor with a unique stator. Such a stator has a double-wound (or four-layer) coil that leads to improved utilization of the motor design space. This facilitates a gain in the use of copper wire by the motor compared to a stator with a single-wound (or two-layer) coil, thus significantly increasing the torque capability of the motor. The stator of the present invention also enables the motor to achieve a higher motor constant and a higher motor efficiency. It should be noted that due to the fixed geometry of the motor, when a double-wound stator is implemented instead of a single-wound stator, the stator coils become thicker, so smaller magnets and / or thinner yokes need to be used. Thus, increasing the number of magnet wires in a double-wound stator comes with a compromise of smaller magnets used in the rotor and / or a reduced yoke thickness. This leads to a decrease in magnetic flux density. However, the effect of more magnet wires more than compensates for the decrease in magnetic flux density due to the smaller rotor magnets and thinner magnetic yokes. In some embodiments, thicker magnet wire may be used in a dual-wound stator to maintain the same coil resistance as a single-wound stator. Such a dual-wound stator has two coils per phase per pole pair connected in the configuration described above. This may increase the motor torque coefficient by about 20% to about 50% over a blood pump using a single-wound stator with one coil per phase per pole pair. In certain embodiments, the motor torque coefficient may be increased by about 25%, about 30%, about 35%, about 40%, or about 45%.

[0021] Furthermore, previous attempts to increase the number of magnet wires in the stators of electric motors have resulted in non-uniform multi-layer stators. The irregular arrangement of wires in such stators leads to randomly wound stators that are too large, especially in thickness. Such randomly wound stators often require mechanical squeezing to reduce the coil thickness by reducing the coil diameter and / or increasing the coil inner diameter before they can be used in an electric motor. In contrast, dual-winding stators according to aspects of the present disclosure allow for sequential placement of magnet wires in each coil of the stator, thereby resulting in a stator with more compact coils. Due to the relatively thin coils of dual-winding stators compared to randomly wound multi-layer stators, no or minimal mechanical squeezing is required prior to use, which preserves the integrity of the wire insulation and enhances motor reliability.

[0022] A description of the stator is included below using the following terms: The stator comprises at least one winding, e.g., an inner winding and an outer winding, electrically connected together. Each of the windings spans 360° around the cross section of the stator. Additionally, each of the windings comprises multiple coils, e.g., coils A, B, and C for a three-phase electric motor, evenly spaced circumferentially around the entire 360° span of the stator. For example, coils A, B, and C may each span 120° around the cross section of the stator. Each coil comprises multiple turns N. For example, each coil may comprise 65 winding turns. Each of the N turns comprises magnet wire with a forward portion extending longitudinally from the proximal end to the distal end of the winding and a return portion extending from the distal end to the proximal end. Each winding (inner or outer) of coils A, B, and C forms a two-layer coil when completed. Thus, the dual-wound stator forms a total of four layer coils.

[0023] FIG. 1 illustrates an exemplary intravascular blood pump 100 for insertion into a patient's heart according to one embodiment of the disclosure. The blood pump 100 includes a motor unit 110 and a pump unit 120 disposed along a longitudinal axis 105. The motor unit 110 includes an electric motor including a stator 140 and a rotor 150 housed within a housing 112. The stator 140 extends along the length of the motor unit 110 from a proximal end 142 to a distal end 143 and includes a wire 144 wound in a particular pattern, which will be described in more detail below. The stator 140 defines a central lumen 145 within which the rotor 150 is positioned. The stator 140 is slotless such that the wire 144 is wound on itself and not on a laminated stator core. For operation of the motor unit 110, electrical supplies 146, 147 provide the necessary electrical connections from the exterior of the pump 100 to the stator 140. Each of the wires 144 may have an insulating coating (not shown), and the stator 140 may be enmolded with a synthetic epoxide resin (also not shown).

[0024] 1, the stator 140 and the housing 112 are depicted as separate components, but it will be understood that the stator 140 may be enclosed within the housing 112 to form a single component. The housing 112 has a proximal end 114 and a distal end 116. The proximal end 114 of the housing 112 is coupled to a distal end 134 of a catheter 130, which may comprise a flexible tube. The catheter 130 has a lumen 132 that extends toward (i.e., proximally) a physician for control and operation of the blood pump 100.

[0025] The rotor 150 comprises a permanent magnet 152 rotatably supported within the lumen 145 of the stator 140 around a shaft 153. The magnet 152 may comprise a cylindrical permanent magnet 152 that surrounds the shaft 153 within the motor unit 110. The shaft 153 extends from the motor unit 110 into the pump unit 120 and facilitates the rotation of the impeller 160 to pump blood. In certain embodiments, the rotor 150 may comprise several permanent magnets attached to the shaft 153 or an electromagnet with its own rotor winding. Additionally, although FIG. 1 illustrates the rotor 150 as rotatable within the stator 140, the electric motor 110 may be configured such that the stator 140 remains stationary around the shaft 153 and the rotor 150 is configured as a cylinder that rotates around the stator 140. The shaft 153 extends along the length of the motor unit 110 and into the cylindrical housing 122 of the pump unit 120. In some embodiments, the shaft 153 may be hollow and include a lumen 154, for example, for the passage of a guidewire.

[0026] The distal end of shaft 153 is coupled to an impeller 160 located within pump housing 122. Interaction between stator 140 and rotor 150 of motor unit 110 generates a torque in rotor 150 causing shaft 153 to rotate, which in turn rotates impeller 160 within cylindrical pump housing 122. When this occurs, blood is drawn into the pump through axial intake opening 124 for axial transport, and the blood exits laterally through opening 126 and flows axially along housing 112. In this manner, pump 100 generates blood flow within the patient's heart.

[0027] The electric motor also includes a yoke 113 housed within the housing 112. The yoke 113 carries the magnetic flux generated by the permanent magnetic poles of the rotor 150. In some cases, the housing 112 may serve as the yoke 113. Since the yoke 113 is the outermost component of the electric motor, its inner diameter limits the size of the stator 140.

[0028] 2A-2D illustrate exemplary winding patterns 210-213 according to one embodiment of the disclosure. Although FIGS. 2A-2D show individual winding turn configurations for different winding patterns, such as wire 142 in FIG. 1, it will be understood that a completed stator, such as stator 140 in FIG. 1, is obtained by axially and angularly disposing multiple wire turns around a longitudinal axis of the motor unit, such as longitudinal axis 105 in FIG. 1. FIGS. 2E-2H illustrate the coil winding patterns for a completed stator for each of the coil winding types in FIGS. 2A-2D, respectively. The horizontal axis of each plot in FIGS. 2E-2H represents the angular position along the circumference of the respective stator, and the vertical axis represents the longitudinal length of the respective stator from the distal end to the proximal end of the stator.

[0029] 2A-2D illustrate exemplary winding patterns for individual turns in a coil used in an electric machine. The winding patterns in FIGS. 2A-2D may be used to form the stator 140 of the motor unit 110 in FIG. 1. FIG. 2A illustrates an individual coil winding pattern 210 in which each wire 214 in the coil extends from a proximal end 221 along the length of the coil to a distal end 225. At the distal end 225, the wire 214 follows the circumference of the stator over a mechanical angle of 180 degrees and returns to the proximal end 221. Because both ends of the wire 214 terminate at the proximal end 221, the coil winding pattern 210 may face end turn stack up issues in that each of the multiple leads must be electrically connected to the stator feedline at the proximal end 221 of the coil winding 210, which in turn may cause congestion and connection issues. The completed coil winding pattern formed by the coils having the turns illustrated in Figure 2A is shown in Figure 2E. Figure 2B shows an individual diamond coil winding pattern 211 with each wire 215 arranged in a bent configuration. Unlike the coil winding pattern 210 in Figure 2A, the diamond coil winding pattern comprises one continuous wire that is wound several times; each completed turn is angularly shifted to form the completed coil winding pattern as shown in Figure 2F. If a bent configuration of the diamond coil winding pattern is employed in the stator, post assembly of each individual phase coil may be required.

[0030] FIG. 2C shows an individual helical coil winding pattern 212 with each wire 216 arranged in an elliptical configuration. The helical coil winding pattern 212 is similar to the diamond coil winding pattern 211 in FIG. 2B, but without the bends, which simplifies the coil winding process. The helical coil winding is a one-step winding that can be easily formed without the need for a post-assembly step. A completed coil winding pattern with the helical coil winding pattern shown in FIG. 2C is shown in FIG. 2G. FIG. 2D shows an individual hybrid coil winding pattern 213 with a coil winding that is a mix of the coil winding as shown in FIG. 2A and the diamond coil winding as shown in FIG. 2B. Such a hybrid coil winding allows for an optimal ratio of torque and resistance by adjusting the horizontal to vertical aspect ratio of the coil. A completed coil winding with the hybrid coil winding pattern shown in FIG. 2D is shown in FIG. 2H.

[0031] In the following disclosure, each stator utilizes the individual helical coil winding pattern of Figure 2C and the associated completed coil winding pattern of Figure 2G. However, it will be understood that the stators in this disclosure may use any of the winding patterns described with respect to Figures 2A-2D. Additionally, any other winding pattern may be used in some embodiments of the present disclosure.

[0032] 3 and 4 illustrate cross sections of an exemplary stator for use in an electric motor, such as stator 140 of motor unit 110 in FIG. 1. The cross sections of the stator illustrated in FIGS. 3 and 4 are taken along line X-X' shown in FIG. 1. FIG. 3 illustrates a stator 300 with one coil per phase per pole pair for use in a three-phase electric motor having one pole pair. In this arrangement, stator 300 is a single-wound stator (or a two-layer coil stator). In this disclosure, the three phases of the electric motor are referred to as phases A, B, and C. In single-wound stator 300, each phase has one coil - coil 310 (labeled "A") for phase A, coil 311 (labeled "B") for phase B, and coil 312 (labeled "C") for phase C. Each of the coils 310-312 comprises a winding having a plurality of N turns, where N is an integer and N>1, and each coil has the same number of turns. The windings are formed from wire wound in a unique manner, such as that described with respect to Figures 2A-2D, resulting in each coil having a beginning and an end, as shown by leads 320-325 in Figure 3. In some embodiments, the windings are formed from insulated magnet wire. Aspects of the disclosure are described with respect to a stator having a helical coil as illustrated in Figures 2C and 2G, although it will be understood that any winding type may be used.

[0033] As seen in FIG. 3, the angular distribution of the coils 310-312 is such that they are equally distributed around the stator 300, with each coil spanning 120 mechanical degrees around the circumference of the cross section of the stator 300. Although the stator 300 is used in a three-phase electric motor with one coil per pole pair, for a typical electric motor with n phases and p pole pairs, each coil of a single-winding stator with one coil per phase per pole pair spans a mechanical angle of 360 / (np) degrees around the circumference of the cross section of the stator. With respect to the axial distribution of the coils around the longitudinal axis of the single-winding stator 300, the windings of the coils 310-312 are configured to extend longitudinally from a proximal end of the stator 300 (such as the proximal end 142 of the stator 140 in FIG. 1 ) to a distal end (such as the distal end 143 of the stator 140 in FIG. 1 ) and back to the proximal end. In this manner, each of the coils 310-312 of the stator 300 effectively comprises a single winding. In the configuration shown in Figure 3, the leads for each of the coils 310-312 are located at the proximal end of the stator 300 for easy connection to an electrical power supply to an electric motor, such as the electrical power supplies 146, 147 shown in Figure 1.

[0034] It should be noted that because of the manner in which the single-wound stator is formed, the leads 320-325 for each coil 310-312 are located at either end of the respective coil span. For example, coil A is formed by winding wire in a first direction (e.g., counterclockwise) around the circumference of the stator around a 120° span of the coil from a first end 320 to the end of the coil span where the magnet wire forms a second end 321. Further, in single-wound stator 300, coil A is formed in its entirety before coils B and C are formed.

[0035] Figure 4 shows a stator 400 with two coils per phase per pole pair for use in a three-phase electric motor having one pole pair according to one embodiment of the disclosure. In this arrangement, stator 400 is a double-wound stator (or a four-layer coil stator), and when implemented with the individual helical coil winding pattern depicted in Figure 2C, stator 400 is a double helical wound stator similar to the completed winding illustrated in Figure 2G. In stator 400, each phase A, B, and C of the three-phase electric motor includes two coils. Thus, phase A includes coil 410 (labeled "A1") and coil 411 (labeled "A2"), phase B includes coil 412 (labeled "B1") and coil 413 (labeled "B2"), and phase C includes coil 414 (labeled "C1") and coil 415 (labeled "C2"). Further, as shown in FIG. 4, stator 400 has an inner winding including coils A1, B1, and C1, and an outer winding including coils A2, B2, and C2.

[0036] With reference to the single-wound stator 300 in FIG. 3, the dual-wound stator 400 of the present disclosure is a thicker coil and may have a smaller inner diameter and / or a larger outer diameter than the single-wound stator 300. In certain embodiments, thicker magnet wire is used in the dual-wound stator 400 compared to the wire used in the single-wound stator 300 to maintain comparable coil resistance. Thus, if each coil 310-312 of the single-wound stator 300 includes a winding having N turns, where N is an integer and N≧1, then the coils for each phase A, B, and C in the dual-wound stator 400 include a winding having about 1.5N turns to about 2N turns, with each coil A1, B1, and C1 in the inner winding having the same number of turns, and each coil A2, B2, and C2 in the outer winding having the same number of turns. However, due to the increased diameter of the dual-wound stator 400, it should be noted that each of the coils A2, B2, and C2 in the outer winding has a greater number of turns than each of the coils A1, B1, and C1 in the inner winding. It should be noted that the dual-wound stator 400 is implemented with a thicker magnet wire to lower the coil resistance, resulting in a dual-wound stator having about 1.5N turns to about 2N turns. As explained above, the coils 410-415 are each formed from a helical winding having a start point and an end point, as shown in FIG. 4 by leads 420-431.

[0037] The angular distribution of the coils 410-415 is such that they are equally distributed around the stator 400, with each coil spanning 120 mechanical degrees around the circumference of the cross section of the stator 400. The stator 400 is used in a three-phase electric motor having two coils per phase per pole pair, but for a general electric motor having n phases and p pole pairs, the stator 400 comprises an inner winding and an outer winding. The inner winding comprises np coils, with one coil from each phase positioned next to a coil from a different phase in phase order for the pole pairs, and the arrangement is repeated around the circumference of the stator for all pole pairs, such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross section of the stator. The inner winding provides an outer surface on which the coils of the outer winding are formed. The outer winding also comprises n coils arranged on the outer surface of the inner winding, and the coils of each phase of the outer winding are circumferentially aligned with the coils of the inner winding having the same phase for each pole pair, such that each coil of the outer winding also spans a mechanical angle of 360 / (n) degrees around the cross section of the stator.

[0038] The winding pattern of the individual coils A1, B1, and C1 in the dual-winding stator 400 is the same as that of the individual coils A, B, and C in the single-winding stator 300. However, in the dual-winding stator 400, after the inner winding is formed, the windings of the coils 411, 413, 415 forming the outer winding are wound on the outer surface of the coils 410, 412, 414 forming the inner winding, extending longitudinally from the proximal end of the stator 400 to the distal end and back to the proximal end. In this manner, the inner and outer windings each effectively comprise two layers of wire, and are thus referred to as a four-layer coil stator. The leads for each coil 410-415 are located at the proximal end of the stator 400 for easy connection to a power supply to an electric motor, such as the power supplies 146, 147 shown in FIG. 1.

[0039] It should be noted that because of the manner in which the dual-wound stator 400 is formed, the leads 420-421, 424-425, and 428-429 for the coils 410, 412, and 414 of the inner winding, respectively, and the leads 422-423, 426-427, and 430-431 for the coils 411, 413, and 415 of the outer winding, respectively, are located at either end of the span of the respective coils. For example, coil A1 is formed by winding the coil in a first direction (e.g., counterclockwise) around the circumference of the stator around a 120° span of the coil from a first end 420 to the end of the coil span where the magnet wire forms a second end 421. After coil A1 is formed, the coils that make up the remainder of the inner winding (i.e., coils B1 and C1) are formed. Only once the inner winding is completely formed do the coils that make up the outer winding begin to be formed. Thus, after coils A1, B1, and C1 are formed, coils A2, B2, and C2 are formed. Coil A2 is formed by winding the coil in a first direction (e.g., counterclockwise) around the circumference of the stator around a 120° span of the coil from a first end 422 to the end of the coil span where the magnet wire forms a second end 423. After coil A2 is formed, the coils that make up the remainder of the outer winding are formed. The winding sequence of the present disclosure results in precisely ordered windings of wire to achieve the most compact four-layer coil stator possible. This preserves the integrity of the wire forming each coil, as will be described in more detail in the following section with respect to FIGS. 9A-9B.

[0040] It should be noted that the dual-wound stator 400 is at least twice as thick as the single-wound stator 300. This means that the dual-wound stator 400 may have a smaller inner diameter and / or a larger outer diameter than the single-wound stator 300. When the dual-wound stator 400 is used in an electric motor, fixed dimensions within the electric motor necessitate smaller magnets and / or thinner yokes, both of which reduce the magnetic flux density and therefore the motor torque coefficient and motor efficiency. However, the benefits of the increased number of coil winding turns in the dual-wound stator 400 compared to the single-wound stator 300 outweigh the smaller magnets and / or thinner yokes, thereby resulting in a significant increase in the motor torque coefficient and motor efficiency.

[0041] FIG. 5 illustrates an exemplary cross section 500 of the electric motor 110 of the blood pump 100 of FIG. 1 using a dual-winding stator 400 in a three-phase, two-pole electric motor. For clarity, the windings forming the coils 410-415 have been omitted from FIG. 5. The interaction of the current flowing in the coils of the stator 400 with the magnetic flux density of the two-pole rotor during operation is described with reference to FIG. 5. As described with respect to FIG. 1, in use the rotor 150 is in constant rotation. FIG. 5 depicts the position of the rotor 150 at the moment when the rotor is in the position shown in the figure. In the position shown, the permanent magnet rotor 150 generates a magnetic flux density B, and each of the coils 410-415 carries a current that may be directed vertically (into or out of the page). According to the Lorentz force law, the interaction between the magnetic flux density B and the longitudinal length L of the conductive wire in a direction perpendicular to the magnetic flux density B generates a torque T in the rotor 150 causing it to rotate, which is determined by the following equation: TIFF2025026872000001.tif4128 formula, TIFF2025026872000002.tif3128 is a direction parallel to the longitudinal axis 105 of the rotor 150, TIFF2025026872000003.tif3128 is the radial direction of magnetic flux density B perpendicular to the longitudinal axis 105 of rotor 150, and x represents the cross product of vectors. Thus, current flow in stator 400 causes rotation of rotor 150 about longitudinal axis 105, which in turn causes corresponding rotation of impeller 160 coupled to the distal end of rotor shaft 153. Although with a slight reduction in magnetic flux density B, stator 400 described herein attempts to significantly increase L to increase torque production in the motor.

[0042] The dual-winding stator 400 of the present disclosure increases the number of winding turns of an electric motor compared to a single-winding stator by doubling the number of coils per phase. However, as described with respect to FIGS. 9A-9B, the dual-winding stator of the present disclosure is not solely concerned with doubling the number of coils per phase. Rather, the dual-winding stator 400 of the present disclosure is formed using a unique winding sequence in which the wires forming the coils of the inner winding are formed in sequence first, and then the wires forming the coils of the outer winding are formed in sequence on the outer surface of the inner winding. Such a winding sequence increases the packing density of the coils between the outer diameter of the rotor 150 and the inner diameter of the yoke 113. Thus, the dual-winding stator 400 of the present disclosure significantly increases the L component of equation (1) as the number of conductive wires of the stator 400 increases, and does not require a reduction in the size of the magnets and the thickness of the magnetic yoke.

[0043] As briefly discussed with respect to FIG. 1, the outer diameter of pump 100 is limited by the inner diameter of the catheter used to position the pump within the patient's heart. Currently, the maximum inner diameter of catheters used for Impella® pumps is approximately 14 Fr. Thus, as shown in FIG. 5, the electric motor dimension x + y + z, where x is the radius of rotor 150, y is the thickness of the stator coils, and z is the thickness of yoke 113, is constrained by the inner diameter of the catheter. To increase the magnetic flux density B in the motor, (i) larger permanent magnets may be used (i.e., x is larger), (ii) the coils may be made thinner (i.e., y is smaller), and (iii) a thicker yoke may be used (i.e., z is larger).

[0044] With regard to the dual-wound stator 400 design, when compared to the single-wound stator 300, the motor magnetic flux density B is reduced due to the thicker coils (larger y) of the dual-wound stator and, as a result, the smaller permanent magnets (smaller x) and thinner yoke (smaller z) required by space constraints within the catheter. This reduces the B component in equation (1). However, the increase in L due to the higher number of winding turns on the coils is greater than the reduction in B due to the reasons discussed above. The net effect is an increase in the torque generated in the rotor 150.

[0045] The coils 310-312 in the single-wound stator 300 and the coils 410-415 of the dual-wound stator 400 of the present disclosure may be electrically connected in any configuration for an electric motor, such as, for example, star or delta. FIG. 6A shows the coils 310-312 of the single-wound stator 300 of FIG. 3 connected in an exemplary star configuration 600. The coils 310-312 are represented as their resistances RA, RB, and RC, respectively. In FIG. 6A (and subsequent FIGS. 6B and 6C), "s" represents the beginning lead of the coil, and "e" represents the ending lead of the coil. In the star configuration 600, the end "Ae" of coil 310, the end "Be" of coil 311, and the end "Ce" of coil 330 are connected together. The beginning "As" of coil 310, the beginning "Bs" of coil 311, and the beginning "Cs" of coil 312 are connected to a power supply, such as power supplies 146, 147 of blood pump 100 in Figure 1. In this manner, each branch of star configuration 600 has a single load corresponding to the coils for each phase in single-wound stator 300.

[0046] FIG 6B illustrates an example electrical connection of coils in a dual-winding stator 400 according to one embodiment of the disclosure. FIG 6B illustrates the coils of stator 400 connected in a star configuration with the coils for each phase A, B, and C connected in series, where coils 410-411 are represented as resistances RA1 and RA2, respectively, for phase A, coils 412-413 are represented as resistances RB1 and RB2, respectively, for phase B, and coils 414-415 are represented as resistances RC1 and RC2, respectively, for phase C. As mentioned above, stator 400 includes coils arranged in inner and outer windings. Each of the inner winding coils 410, 412, 414 has N turns, while each of the outer winding coils 411, 413, and 415 has at least N turns; where N is the number of turns in each coil of the stator 300, the total number of winding turns per phase in the dual winding stator 400 may be 1.5 to 2.0 times that of the single winding stator 300. Thus, the electrical resistance per phase of the dual winding stator 400 is higher than that of the single winding stator 300. It should be noted that in some embodiments, thicker magnet wire is used in the dual winding stator 400 to achieve the same resistance as compared to the single winding stator 300.

[0047] It is well known that motor efficiency is determined by the motor constant K, which is defined as m It can be shown by: TIFF2025026872000004.tif7128, k T is the torque coefficient and R is the coil resistance. Furthermore, as is well known, the torque coefficient k T is the torque T per unit current I, and therefore the torque coefficient can be defined using the following relationship: TIFF2025026872000005.tif4128In the formula, B is the magnetic flux density and L is the length of the conductive wire in the direction perpendicular to the magnetic flux density.

[0048] 5, the dual-wound stator 400 of the present disclosure increases the contribution of L by about 1.5 to about 2 times when compared to the single-wound stator 300, while slightly reducing the contribution of B to the torque T generated in the rotor 150 due to the larger y (thicker coils), smaller x (smaller magnets), and / or smaller z (thinner yoke). According to equations (1) and (3), this reduces the motor torque coefficient k T % to about 20% to about 50%. In other embodiments, the motor torque coefficient may be increased by about 25%, about 30%, about 35%, about 40%, or about 45%. Furthermore, since the number of turns per phase in the dual-wound stator 400 is increased compared to the single-wound stator 300, thicker wire is used to achieve the same coil resistance as the single-wound stator 300. Therefore, from equation (2), the dual-wound stator 400 of the present disclosure has a motor constant K m This is expected to increase the motor efficiency.

[0049] As shown in the circuit diagram of FIG. 6B, each branch of the star configuration 650 includes two coils connected in series such that current flows through the coils of the same phase in the same direction; i.e., the two coils are connected in such a manner that the end of one coil is connected to the beginning of the other coil. For example, for phase A, coils 410-411, represented by resistors RA1 and RA2, respectively, are connected such that the end "A1e" is connected to the beginning "A2s". Similarly, the end "B1e" of coil 413 and the beginning "B2s" of coil 414 of phase B, represented by resistors RB1 and RB2, respectively, are connected together, and the end "C1e" of coil 414 and the beginning "C2s" of coil 415 of phase C, represented by resistors RC1 and RC2, respectively, are connected together. A start point "A1s" of resistance RA1 of phase A coil 410, a start point "B1s" of resistance RB1 of phase B coil 412, and a start point "C1s" of resistance RC1 of phase C coil 414 are connected to a power supply, such as power supplies 146, 147 of blood pump 100 in Figure 1. In addition, an end point "A2e" of resistance RA2 of phase A coil 411, an end point "B2e" of resistance RB2 of phase B coil 413, and an end point "C2e" of resistance RC2 of phase C coil 415 are connected together.

[0050] The manner in which the coils 410-415 of the dual-winding stator 400 of the present disclosure are connected is important because it determines how the coils 410-415 interact with the magnetic flux density generated by the rotor 150 during operation of the electric motor. In a star configuration 650 as depicted in FIG. 6B, the direction of current flowing through coil A1 of the stator 400 is the same as the direction of current flowing through coil A2. Similarly, the direction of current flowing through coil B1 of the stator 400 is the same as the direction of current flowing through coil B2, and the direction of current flowing through coil C1 of the stator 400 is the same as the direction of current flowing through coil C2. This means that both coils A1 and A2 that have the same direction of current flowing through them interact with the same pole of the rotor. In addition, both coils B1 and B2 that have the same direction of current flowing through them interact with the same pole of the rotor. Furthermore, both coils C1 and C2 that have the same direction of current flowing through them interact with the same pole of the rotor. That is, the coils of each phase in the dual-winding stator 400 of the present disclosure see the same polarity of magnets for each pole pair of the rotor.

[0051] 6C illustrates a further example electrical connection of coils in a dual-winding stator 400 according to one embodiment of the disclosure. In FIG. 6C, the coils of stator 400 are connected in a star configuration 660, with the coils for each phase A, B, and C connected in parallel such that the current flows through the coils in the same direction. This can be seen in FIG. 6C; for phase A, coils 410-411, represented by resistors RA1 and RA2, respectively, are connected such that end points "A1e" and "A2e" are connected to a central reference terminal, while start points "A1s" and "A2s" are connected to the power supply. Similarly, for phase B, coils 412-413, represented by resistors RB1 and RB2 respectively, are connected such that end points "B1e" and "B2e" are connected to the central reference terminal while start points "B1s" and "B2s" are connected to the power supply, and for phase C, coils 414-415, represented by resistors RC1 and RC2 respectively, are connected such that end points "C1e" and "C2e" are connected to the central reference terminal while start points "C1s" and "C2s" are connected to the power supply.

[0052] Similar to the configuration 650 in FIG. 6B, in the star configuration 660 as depicted in FIG. 6C, the direction of current flowing through coil A1 of the stator 400 is the same as the direction of current flowing through coil A2. Similarly, the direction of current flowing through coil B1 of the stator 400 is the same as the direction of current flowing through coil B2, and the direction of current flowing through coil C1 of the stator 400 is the same as the direction of current flowing through coil C2. This means that both coils A1 and A2 with the same direction of current flowing through them interact with the same pole of the rotor. In addition, both coils B1 and B2 with the same direction of current flowing through them interact with the same pole of the rotor. Furthermore, both coils C1 and C2 with the same direction of current flowing through them interact with the same pole of the rotor. That is, the coils of each phase in the dual-winding stator 400 of the present disclosure encounter the same polarity of the magnets for each pole pair of the rotor.

[0053] FIG. 7 illustrates another example cross section of a dual-winding stator 700 for use in an electric motor having three phases A, B, and C and two permanent magnetic pole pairs N1-S1 and N2-S2 according to one embodiment of the disclosure. According to the general definition above, an electric motor using stator 700 has n=3 and p=2. As discussed with respect to stator 400 in FIG. 4, stator 700 also includes two coils per phase per pole pair, resulting in a total of twelve coils 710-721. In stator 700, due to the presence of two pole pairs in the electric motor, each phase A, B, and C of the three-phase electric motor includes two coils. Thus, phase A includes coils 710-73 (labeled "A1", "A2", "A3", and "A4", respectively), phase B includes coils 714-717 (labeled "B1", "B2", "B3", and "B4", respectively), and phase C includes coils 718-721 (labeled "C1", "C2", "C3", and "C4", respectively). As shown in FIG. 7, stator 700 includes an inner winding of coils and an outer winding of coils. The inner winding comprises six coils; the six coils are arranged in phase order for each pole pair, one coil from each phase next to a coil from a different phase, and the arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans 360° / (np) = 360° / (3)(2) = 60° around the cross section of the stator 700; the inner winding has an outer surface. The outer winding also comprises six coils arranged on the outer surface of the inner winding; the coils of each phase of the outer winding are circumferentially aligned with the coils of the inner winding with the same phase for each pole pair, such that each coil of the outer winding also spans 60° around the cross section of the stator 700. Furthermore, the coils of the same phase for each pole pair may be connected in series or parallel such that the current flowing through the coils is in the same direction.

[0054] Similar to the coils of stator 400, coils 710-721 may be electrically connected in either a star or delta configuration: (i) phase A coils 710-713 are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a phase A branch of the star or delta connection; (ii) phase B coils 714-717 are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a phase B branch of the star or delta connection; and (iii) phase C coils 718-721 are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a phase C branch of the star or delta connection. In such electrical connections, (i) the direction of current flowing through coils A1 and A3 is the same as the direction of current flowing through coils A2 and A4; (ii) the direction of current flowing through coils B1 and B3 is the same as the direction of current flowing through coils B2 and B4; and (iii) the direction of current flowing through coils C1 and C3 is the same as the direction of current flowing through coils C2 and C4. In short, whether the coils of the same phase are connected in series or in parallel, the currents flowing through the coils of the same phase flow in the same direction.

[0055] In this arrangement, the coils A1-A4 have the same direction of current flowing therethrough; where coils A1 and A3 interact with, for example, pole S1, and coils A2 and A4 interact with, for example, corresponding pole S2, which is the same polarity as pole S1, to rotate the rotor. Similarly, the coils B1-B4 have the same direction of current flowing therethrough; where coils B1 and B3 interact with, for example, pole N1, and coils A2 and A4 interact with, for example, corresponding pole N2, which is the same polarity as pole N1, to rotate the rotor. Furthermore, the coils C1-C4 have the same direction of current flowing therethrough; where coils C1 and C3 interact with, for example, pole S2, and coils C2 and C4 interact with, for example, corresponding pole S1, which is the same polarity as pole S2, to rotate the rotor. It should be noted that the coils 710-721 may be driven by, for example, a six-stage DC current controller that provides alternating current to the coils 710-721 in pairs of two phases at a time, such that the coils from each phase in turn generate torque in the rotor, thereby causing continuous rotation of the rotor.

[0056] 8 illustrates a further example cross-section of a dual-winding stator 800 for use in an electric motor having five phases A, B, C, D, and E and one permanent magnetic pole pair NS according to one embodiment of the present disclosure. Per the general definitions above, an electric motor using stator 800 has n = 5 and p = 1. As discussed with respect to stators 400 and 700, stator 800 also includes two coils per phase per pole pair, resulting in a total of ten coils 810-819. Phase A includes coils 810-811 (labeled "A1" and "A2", respectively), phase B includes coils 812-813 (labeled "B1" and "B2", respectively), phase C includes coils 814-815 (labeled "C1" and "C2", respectively), phase D includes coils 816-817 (labeled "D1" and "D2", respectively), and phase E includes coils 818-819 (labeled "E1" and "E2", respectively). As shown in FIG. 8, stator 800 includes an inner winding of coils and an outer winding of coils. The inner winding has five coils; the five coils are arranged in phase order for each pole pair, one coil from each phase next to a coil from a different phase, and the arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans 360° / (np) = 360° / (5)(1) = 72° around the cross section of the stator 800; the inner winding has an outer surface. The outer winding also has five coils arranged on the outer surface of the inner winding; the coils of each phase of the outer winding are circumferentially aligned with the coils of the inner winding with the same phase for each pole pair, such that each coil of the outer winding also spans 72° around the cross section of the stator 800. Furthermore, the coils of the same phase for each pole pair are connected in series or parallel such that the currents flowing through the coils are in the same direction.

[0057] Similar to the coils of stators 400 and 700, coils 810-819 may be electrically connected in either a star or delta configuration as follows: (i) coils 810-811 for phase A are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a branch of phase A of the star or delta connection; (ii) coils 812-813 for phase B are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a branch of phase B of the star or delta connection; (iii) coils 813 for phase C are connected in series or parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a branch of phase B of the star or delta connection; (iv) coils 816-817 for phase D are connected in series or in parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a branch for phase D of the star or delta connection; and (v) coils 818-819 for phase E are connected in series or in parallel with a start terminal of one coil connected to an end terminal of an adjacent coil along a branch for phase E of the star or delta connection. In such electrical connections, (i) the direction of current flowing through coil A1 is the same as the direction of current flowing through coil A2; (ii) the direction of current flowing through coil B1 is the same as the direction of current flowing through coil B2; (iii) the direction of current flowing through coil C1 is the same as the direction of current flowing through coil C2; (iv) the direction of current flowing through coil D1 is the same as the direction of current flowing through coil D2; and (v) the direction of current flowing through coil E1 is the same as the direction of current flowing through coil E2.

[0058] In this arrangement, coils A1-A2 have the same direction of current flowing therethrough; where coils A1-A2 interact with, say, pole N at any given moment. Similarly, coils for each of the other phases B-E also interact with the same polarity of magnetic flux from the rotor at any given moment; coils for each phase have the same direction of current flowing therethrough at any given moment. Coils 810-819 are driven by a motor controller that provides current to the coils of multiple phases at a time. Thus, the coils for each phase in turn generate torque in the rotor, thereby causing the rotor to rotate continuously.

[0059] Table 1 shows representative data for two blood pumps having electric motors with single and double helix wound stators, respectively. Specifically, the single helix wound stator is similar to the single wound stator 300 as described above, implemented with a helical winding type as shown in FIG. 2C. The double helix wound stator is similar to the double wound stator 400 as described above, also implemented with a helical winding type as shown in FIG. 2C. As can be seen in the table, the double helix wound stator has an increased coil resistance of 5.40 Ω / phase and a torque coefficient of 1.236×10 compared to the single helix wound stator. -3 N·m / A, or 40.5% increase from a single helical wound stator. The results in Table 1 confirm that the dual-wound stator according to embodiments of the present disclosure reduces the Joule heating of the coil by 40%, while a motor using such a dual-wound stator produces the same torque to drive the pump compared to a motor using a single-wound stator. It should be noted that blood pumps using the above-described stator with two coils per phase per pole pair are configured to operate at flow rates of about 1.0 lpm and about 6.0 lpm; here "lpm" stands for liters per minute.

[0060] TIFF2025026872000006.tif47131 (Table 1) Performance of blood pumps with various stator coil configurations

[0061] As explained above, increasing the number of magnet wires from a single-wound stator to a double-wound stator reduces the Joule heating of the coils for the same output torque, thus improving the overall efficiency of the motor. However, a conventional embodiment of increasing the number of winding turns is described with reference to FIG. 9A. FIG. 9A shows an example stator 900 having multiple magnet wire layers, where the amount of conductor in the stator 900 is increased from a two-layer stator. The stator 900 is suitable for use in a three-phase electric motor having phases A, B, and C. As with the stators described above, phase A comprises coil "A", phase B comprises coil "B", and phase C comprises coil "C". As can be seen, the amount of conductor in each coil of the stator is increased by simply increasing the number of turns of magnet wire in each coil in a random manner, where the wire is wound without any precision or regularity. For example, as shown in FIG. 9A, each of coils A, B, and C is formed by randomly laying turns of magnet wire starting with turn 1 and ending with turn 65 according to the numbers shown in the figure. Because the goal is to pack a specific number of magnet wire into each coil, the turns are laid randomly without any order within each coil. Turns 1-4, for example, are spaced apart from one another as they are laid out to form each coil. This leads to random packing of magnet wire within each coil, but the random laying is a poor use of space because it results in, for example, the formation of large gaps 910 as the coils are formed; the gaps that are formed may be occupied by turns wound later in the winding sequence. This inefficient use of space within each coil results in a stator 900 that is thick and oversized.

[0062] Figure 10A illustrates an example randomly wound multi-layer stator 900 formed using the winding sequence described with respect to Figure 9A. The random placement of the wires forming the stator 900 is seen in Figure 10A, with the magnet wires being irregular and over-overlapping. This contributes to an irregular winding pattern on the exterior of the stator, as can be seen in the appearance of the exterior of the stator shown in Figure 10A.

[0063] A randomly wound multi-layer stator 900 that is too large presents several problems. First, the stator would have to be mechanically squeezed to fit within the size constraints of the motor stator. Mechanical squeezing may reduce the thickness of the stator 900 to fit within the yoke of a motor having a fixed inner diameter. Such mechanical squeezing is an additional post-processing step required after the formation of the multi-layer stator 900. Second, mechanical squeezing presents a risk to the integrity of the electrical insulation of the magnet wire within each coil of the stator 900 because the force applied to mechanically squeeze the multi-layer stator may damage the insulation around each magnet wire. Such damage to the magnet wire insulation may result in short circuits within and / or between the coils during operation. It will be appreciated that if the randomly wound multi-layer stator 900 is not squeezed, the magnet size and / or yoke thickness would have to be reduced, which would reduce the magnetic flux density B through the electric motor.

[0064] FIG. 9B illustrates an exemplary stator 950 having four magnet wire layers formed as uniformly wound coils according to one embodiment of the disclosure. The four-layer coil stator 950 is similar to the dual-winding stator 400 in FIGS. 4 and 5. As described above, the stator of the disclosure includes an inner winding 960 and an outer winding 965. As shown in FIGS. 4 and 5, each of the inner winding and the outer winding includes a coil. Furthermore, each of the inner winding and the outer winding includes two magnet wire layers formed as a coil. Here, each of the coils A1, A2, B1, B2, C1, and C2 shown in FIG. 9B is formed by winding magnet wire in an ordered sequence along a 120° span around the cross section of the respective coil stator between the proximal end of the stator, extending longitudinally toward the distal end and returning to the proximal end, using any of the coil winding patterns shown in FIGS. 2E-2H.

[0065] When the magnet wire is wound from the proximal end to the distal end of the stator to form the first turn (e.g., turn labeled "1") in each of the innerwinding coils, a forward portion of the magnet wire for turn 1 is formed in a first layer, and when the magnet wire is wound back from the distal end to the proximal end, a return portion of the magnet wire for turn 1 (labeled "X") is formed in a second layer radially outwardly adjacent to the first layer, where adjacent means "immediately radially next to" (i.e., with nothing in between). Thus, the first turn is formed by a continuous copper wire wound from the proximal end of the stator to the distal end of the stator (the forward wire portion disposed in the first layer) and from the distal end of the stator to the proximal end of the stator (the return wire portion disposed in the second layer, labeled "X"). This is shown in the cross section of FIG. 9B where the outgoing wire portion of turn 1 has a corresponding return wire portion X disposed immediately adjacent and radially outward from the outgoing wire portion. This results in coils having first and second layers in each of the inner winding 960 and outer winding 965 of the stator 950 as shown in the cross section of FIG. 9B. This arrangement of magnet wire is seen in the cross section of the stator 950 in FIG. 9B; the turns of the inner winding 960 are precisely aligned in the order turn 1 through turn 31 for each of the coils A1, B1, and C1 in a counterclockwise direction along the span of the respective coil from 0° to 120°. As the outgoing wire portion of each turn is aligned in the first layer, the corresponding return wire portion is automatically aligned in the second layer, immediately adjacent and radially outward from the outgoing wire portion. Thus, for each turn, the outgoing wire portion (in the first layer) and the corresponding return wire portion (in the second layer) are formed before the turns of the remaining portion of the following coil are formed. Each turn in each coil is formed immediately adjacent to the turn previously formed; that is, each turn is formed immediately next to the previous turn with nothing in between.

[0066] As a result of the precise placement of the turns in the stator 950, the inner winding 960 forms a uniform outer surface onto which the wire of the outer winding 965 is placed. Thus, after all coils A1, B1, and C1 of the inner winding are formed, the coils A2, B2, and C2 of the outer winding are formed on the uniform outer surface of the inner winding in a similar manner as the inner windings are formed. For each of the coils of the outer winding, a first turn (e.g., the turn labeled "32") is formed from the proximal end to the distal end of the stator, with the outward portion of the magnet wire of the first turn 32 formed in a third layer, and a return portion of the magnet wire of the first turn 32 (labeled "Y") formed in a fourth layer adjacent to the third layer radially outward as the magnet wire is wound back from the distal end to the proximal end. Thus, the first turn 32 of the outer winding is formed by a continuous magnet wire wound from the proximal end of the stator to the distal end of the stator (the outward wire portion located in the third layer) and from the distal end of the stator to the proximal end of the stator (the return wire portion located in the fourth layer, labeled "Y").

[0067] This arrangement of magnet wire can be seen in the cross section of stator 950 in FIG. 9B; the turns of the outer winding 965 are precisely ordered from turn 32 to turn 65 for each of coils A2, B2, and C2 in a counterclockwise direction along the 120° span of the respective coil. In this manner, turn 32 of the outer winding is radially aligned with turn 1 of the inner winding, and turn 65 of the wire winding is radially aligned with turn 31 of the inner winding. It should be noted that the stators of the present disclosure have outer windings with more turns than the inner windings due to the larger diameter of the outer windings compared to the inner windings. For example, in the dual-wound stator 950 of FIG. 9B, the outer winding has 34 turns and the inner winding has 31 turns. As a result, stator 950 has magnet wire ordered in a tightly packed arrangement compared to the irregular arrangement of magnet wire in the randomly wound multi-layered winding stator 900. The dual-wound stator 950 is more compact and therefore has a smaller thickness compared to the random-wound multi-layer stator 900 .

[0068] An exemplary winding sequence for forming stator 950 may have the following order: (1) form turns 1-31 for coil A1; (2) form turns 1-31 for coil B1; (3) form turns 1-31 for coil C1; (4) form turns 32-65 for coil A2 on the outer surface of coil A1; (5) form turns 32-65 for coil B2 on the outer surface of coil B1; and (6) form turns 32-65 for coil C2 on the outer surface of coil C1. As previously discussed, each turn includes a go wire portion and a return wire portion that is automatically positioned radially adjacent to the go wire portion.

[0069] Servo motors are used to ensure that the turns are precisely sequenced along the span of each stator. It should be noted that each coil in the inner and outer windings of stator 950 has a pair of leads (such as leads 420-421 for coil A1 in FIG. 4) for connecting to power supplies 146-147 of electric motor 100.

[0070] In some embodiments, to minimize the increase in coil resistance of a double-wound stator compared to a single-wound stator, thicker wire may be used for the coils forming the inner and outer windings to achieve a resistance equivalent to that of a single-wound stator.

[0071] FIG. 10B illustrates an example stator formed using the winding sequence described with respect to FIG. 9B according to aspects of the disclosure. As can be seen, the stator in FIG. 10B has precisely positioned wires, which results in a uniform outer diameter along the length of the stator. When assembling an electric motor with the four-layer coil stator of FIG. 9B, minimal mechanical squeezing of the stator is believed to be required. Because minimal mechanical squeezing is required, the risk of damaging the insulation of the wires forming coils A1, A2, B1, B2, C1, and C2 is minimized, thereby increasing the reliability of the dual-wound stator 950.

[0072] It should be noted that for the randomly wound multilayer stator 900 in FIG. 9A, mechanical squeezing can only reduce the thickness of the stator to a limited extent. Therefore, even after mechanical squeezing, the randomly wound multilayer stator 900 may still be too thick for the yoke used in the electric motor compared to the dual-winding stator 950. To alleviate this issue, in some embodiments, a thinner yoke is used in the randomly wound multilayer stator 900 compared to the dual-winding stator 950 to preserve the outer diameter of the motor so that it can be integrated with other components that work with the motor, such as the 14 Fr catheter through which the Impella® runs. In addition, smaller magnets may have to be used in the randomly wound multilayer stator 900 compared to the dual-winding stator 950.

[0073] Compared to an electric motor with a dual-winding stator 950, in an electric motor with a random-wound multilayer stator 900, a thinner yoke and / or smaller magnets reduce the magnetic flux density B. As shown in Figures 9A and 9B, both the random-wound multilayer stator 900 and the dual-winding stator 950 have the same number of winding turns. This means that both stators 900, 950 have the same contribution of L to the motor torque T, according to equation (1). Compared to an electric motor with a dual-winding stator 950, in an electric motor with a random-wound multilayer stator 900, the magnetic flux density B is lower for the same length L of conductive wires, resulting in a lower motor torque and a lower motor efficiency.

[0074] 11 illustrates an exemplary method 1100 of forming a dual-winding stator, such as stator 400 described above, according to one embodiment of the disclosure. Method 1100 is suitable for forming a dual-winding stator for use in a slotless permanent magnet motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3. Method 1100 begins at step 1110, where an inner winding (such as inner winding 960 in FIG. 9B ) is formed that has np coils. In the inner winding, one coil from each phase is positioned next to a coil from a different phase in phase order per pole pair, and the arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross section of the dual-winding stator. In some embodiments, each winding comprises two layers of wire each extending longitudinally along the length of the stator; the wires in each winding are disposed immediately adjacent to each other in sequence along the span of each winding. The inner winding has an outer surface when completed.

[0075] After completion of the inner winding, the method proceeds to step 1120 where an outer winding is wound, for example the outer winding 965 in FIG. 9B. Like the inner winding, the outer winding also comprises np coils arranged on the outer surface of the inner winding, with the coils of each phase of the outer winding being circumferentially aligned with the coils of the inner winding having the same phase per pole pair, such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the dual-winding stator. Like the inner winding, in some embodiments, each winding comprises two layers of wire each extending longitudinally along the length of the stator; the wires in each winding are arranged immediately next to each other in sequence along the span of each coil. In the arrangement described above, the inner winding and the outer winding of the dual-winding stator 950 share the same angular boundaries.

[0076] Once the inner and outer windings are complete, in step 1130, the coils of the same phase for each pole pair are electrically connected so that the currents flowing through the coils of the same phase are in the same direction.

[0077] In summary, the dual-wound stator of the present disclosure (e.g., stator 400) improves motor efficiency when compared to a single-wound stator (e.g., stator 300) because of the trade-off between rotor magnet size, yoke thickness, and number of winding turns in each stator. This increase in efficiency in the motor is achieved by increasing the motor torque coefficient by about 20% to about 50% while achieving comparable stator resistance. In certain embodiments of the present disclosure, the motor torque coefficient may be increased by about 25%, about 30%, about 35%, about 40%, or about 45%. Additionally, the dual-wound stator of the present disclosure (e.g., stator 950) improves motor reliability compared to a random-wound multi-layer stator (e.g., stator 900) because minimal post-mechanical squeeze processing is required due to the compact arrangement of wires in the dual-wound stator. Since minimal mechanical squeeze is required, there is no resulting damage to the wire insulation in a dual wound stator, unlike a random wound multilayer stator where excessive mechanical squeeze is required.

[0078] From the foregoing description and with reference to the various drawings, one skilled in the art will recognize that certain modifications may also be made to the present disclosure without departing from the scope of the present disclosure. It should be understood that the device described herein is shown in the context of a dual-wound stator for an electric motor for a blood pump, but may be applied to other systems in which an electric motor with increased torque and high motor efficiency is desired. Although the drawings show certain aspects of the present disclosure, the disclosure is not intended to be limited thereto; the disclosure is intended to be as broad as the art will permit, and the specification is intended to be so read. Thus, the foregoing description should not be considered as limiting, but merely as illustrative of certain aspects. Other modifications within the scope and spirit of the appended claims will occur to those skilled in the art.

[0079] It will be understood that in the above disclosure, the term "about" should be taken to mean ±20% of the stated value. In addition, the term "electric motor" should be taken to be synonymous with the term electric machine, as is well known in the art. Furthermore, the term "adjacent" should be taken to mean immediately adjacent with nothing in between. For example, object / feature P is adjacent to object / feature Q when there is no inclusion between them. All angle measures (with units of degrees) should be taken as mechanical angles unless otherwise stated. In the above-mentioned aspects, the wire used for the stator windings may comprise any material, such as copper. In some embodiments, the wire may be insulated.

[0080] Variations and modifications will occur to those skilled in the art after reviewing this disclosure. The features of the present disclosure may be implemented in any combination and subcombination (including multiple subordinate combinations and subcombinations) with one or more other features described herein. The various features described or illustrated above, including components thereof, may be combined or integrated into other systems. Additionally, certain features may be omitted or not implemented.

[0081] Examples of modifications, substitutions, and variations are ascertainable by one of ordinary skill in the art and can be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made a part of this application.

Claims

1. 1. An intravascular blood pump for insertion into a patient's heart, comprising: an elongated housing having a proximal end connected to the catheter and a distal end coupled to the pump, the housing having a longitudinal axis; a slotless permanent magnet motor contained within the housing, the motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3, the motor comprising: a stator having 2np coils extending along a longitudinal axis of the housing and wound to form two coils per phase per pole pair; an innerwinding comprising np coils arranged in a phase order per pole pair, one coil from each phase next to a coil from a different phase, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the innerwinding spans a mechanical angle of 360 / (np) degrees around a cross section of the stator, the innerwinding having an outer surface; an outer winding also comprising np coils disposed on the outer surface of the inner winding, the coils from each phase in the outer winding being circumferentially aligned with the coils from the inner winding having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator; A stator comprising: A motor and the coils of the same phase for each pole pair are electrically connected such that the currents flowing through the coils are in the same direction; and a magnet supported for rotation upon magnetic interaction with the stator; The pump further comprises:

2. 2. The intravascular blood pump of claim 1, wherein each coil of the inner winding and each coil of the outer winding comprises two layers of magnet wire each extending longitudinally along the length of the stator.

3. 3. The intravascular blood pump of claim 2, wherein the magnet wires in each coil are positioned next to each other in sequence along the span of the coil.

4. 2. An intravascular blood pump as claimed in any one of the preceding claims, wherein the inner winding of the coil establishes a uniform surface onto which the outer winding of the coil is superimposed.

5. 10. An intravascular blood pump as claimed in any one of the preceding claims, wherein the coils of one phase are electrically connected to the coils of the other phase in either a star or delta configuration.

6. 6. The intravascular blood pump of claim 5, wherein the coils of each phase are connected either in series or in parallel.

7. 10. The intravascular blood pump of claim 9, wherein each of the 2np coils has a coil winding pattern selected from the group consisting of a helical winding pattern, a diamond winding pattern, and a hybrid winding pattern.

8. 10. An intravascular blood pump as claimed in any preceding claim, wherein the motor comprises a three phase, one pole pair machine.

9. 10. An intravascular blood pump as claimed in any one of the preceding claims, wherein the motor comprises a 6 coil 2 pole machine, each coil spanning a mechanical angle of 120 degrees around the cross section of the stator.

10. 2. The intravascular blood pump of claim 1, wherein the rotor pumps blood at a flow rate of about 1 lpm to about 6 lpm.

11. A slotless permanent magnet electric motor having p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3, the motor having a longitudinal axis; and A stator having 2np coils extending along the longitudinal axis of the housing and wound to form two coils per phase per pole pair. an innerwinding comprising np coils arranged in a phase order per pole pair, one coil from each phase next to a coil from a different phase, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the innerwinding spans a mechanical angle of 360 / (np) degrees around a cross section of the stator, the innerwinding having an outer surface; an outer winding also comprising np coils disposed on the outer surface of the inner winding, the coils from each phase in the outer winding being circumferentially aligned with the coils from the inner winding having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator; A stator comprising: the coils of the same phase for each pole pair are electrically connected such that the currents flowing through the coils are in the same direction; and a magnet supported for rotation upon magnetic interaction with the stator; A motor further comprising:

12. 12. The electric motor of claim 11, wherein each coil of the inner winding and each coil of the outer winding comprises two layers of magnet wire each extending longitudinally along the length of the stator.

13. 13. An electric motor as claimed in any one of claims 11 to 12, wherein the magnet wires in each coil are positioned next to each other in sequence along the span of the coil.

14. 14. The electric motor of claim 11, wherein an inner winding of the coil establishes a uniform base upon which an outer winding of the coil is superimposed.

15. 15. The electric motor of claim 11, wherein the coils of one phase are electrically connected to the coils of the other phase in either a star or delta configuration.

16. 16. The electric motor of claim 15, wherein the two coils per phase are connected either in series or in parallel.

17. 17. The electric motor of claim 11, wherein each coil of the 2np coils has a coil winding pattern selected from the group consisting of a helical winding pattern, a diamond winding pattern, and a hybrid winding pattern.

18. 18. The electric motor of claim 11, wherein the motor comprises a three-phase, two-pole machine.

19. 19. The electric motor of any one of claims 11 to 18, wherein the motor comprises a 6 coil, 2 pole machine, each coil spanning a mechanical angle of 120 degrees around the cross section of the stator.

20. 20. The electric motor of any one of claims 11 to 19, wherein the rotor pumps blood at a flow rate of about 1 lpm to about 6 lpm.

21. 1. A method for forming a stator for use in a slotless permanent magnet motor, comprising: the motor has p pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3; the stator extends longitudinally and includes 2n coils wound to form two coils per phase per pole pair; The method comprises: forming an inner winding comprising np coils arranged in a phase order per pole pair, one coil from each phase next to a coil from a different phase, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around a cross section of the stator, the inner winding having an outer surface; forming an outer winding also comprising np coils disposed on the outer surface of the inner winding, the coils of each phase in the outer winding being circumferentially aligned with the coils of the inner winding having the same phase for each pole pair such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross section of the stator; and electrically connecting the coils of the same phase for each pole pair so that current flows through the coils in the same direction. A method comprising:

22. forming coils on the inner and outer windings such that each coil comprises two layers of magnet wire each extending longitudinally along the length of the stator.

22. The method of claim 21, comprising:

23. 23. The method of claim 22, wherein the magnet wires in each coil are positioned immediately adjacent to one another in sequence along the span of the coil.

24. connecting the coils of one phase with the coils of another phase in either a star or delta configuration The method of any one of claims 21 to 23, comprising:

25. Connecting the coils of each phase either in series or in parallel The method of any one of claims 21 to 24, comprising:

26. forming each of the 2np coils with a coil winding pattern selected from the group consisting of a spiral winding pattern, a diamond winding pattern, and a hybrid winding pattern. The method of any one of claims 21 to 25, comprising:

27. 27. The method of any one of claims 21 to 26, wherein the stator is suitable for use in a motor having three phases and one pole pair.

28. 28. The method of any one of claims 21 to 27, wherein the stator is suitable for use in a 6 coil, 1 pole pair motor, each coil spanning a mechanical angle of 120 degrees around the cross section of the stator.

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